Poplar named ‘Shinsei’

ABSTRACT

A new and distinct poplar clonal cultivar,  Populus nigra  L.× P. maximowiczii  A. Henry, is described. The cultivar results from a controlled pollination using a male  P. maximowiczii  from Hokkaido, Japan and a female  P. nigra  of unknown parentage. Both named parents are unpatented cultivars. The new cultivar is characterised by a narrow crown form, dark green foliage, high resistance to leaf rusts and anthracnose, and low palatability to possums.

Genus and species of plant claimed: Populus nigra×P. maximowiczii.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of New Zealand PVR Application POP006,filed Jun. 25, 2001.

BACKGROUND OF THE INVENTION

The genus Populus consists of 30-40 named species many of which are ableto hybridise with other species (within this genus). Poplars occurnaturally throughout most parts of the temperate and cold regions of theNorthern Hemisphere and have a long history of use by many societies inthese areas.

A poplar breeding programme has been operating in New Zealand since 1968with the aim of producing poplar varieties that are climatically suitedto, and appropriate for end uses in New Zealand. This variety (or clonalcultivar) originated from this breeding programme from a controlledpollinated cross made in 1985.

This clonal cultivar has been vegetatively propagated (as unrooted 25 cmcuttings) from the original seedling identified by the code NZ85-069-002. It has subsequently been vegetatively propagated as unrootedcuttings (25 cm), stakes (1 m) and poles (2 m-3 m).

It has been determined from observations of plantings of the abovematerial that the characteristics described herein hold true to formthrough successive propagations.

SUMMARY OF THE INVENTION

The clonal cultivar was created as a seedling in 1985 from a controlledpollinated cross between a female P. nigra (identified as P. nigra‘LP1’) and pollen from a male P. maximowiczii (itself being an openpollinated seedling, from a known female parent, from Hokkaido Japan andidentified as P. maximowiczii ‘73-010-072’.

The cross was carried out at the National Plant Materials Centre, StacesRoad, Aokautere, Palmerston North, New Zealand. The resulting seedlingswere planted out in nursery beds at the Centre. The first vegetativepropagation was from hardwood cuttings of dormant wood, this was alsocarried out at the National Plant Materials Centre in 1985. Followingselections for further trial, cuttings were bulked up and a gene poolplanting was established in 1990. Field trial plantings commenced in1998.

The tree is characterised by good apical dominance resulting in astraight stem, with a steep branch angle giving a narrow crown form. Theclonal cultivar shows high resistance to the rusts Melampsoralarici-populina and M. medusae and also to leaf anthracnose Marssoninabrunnea. It also exhibits low palatability to possums (Trichosurusvulpecula).

In a New Zealand context this gives a distinctive variety compared withprevious releases by combining narrow crown form with high pest anddisease resistance. This clonal cultivar has been named Shinsei.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows (from left to right) upper surfaces of leaves from: 1) Afully illuminated long branch from a one-year-old cutting and, 2) afully illuminated short branch from an eleven-year-old tree.

FIG. 2 shows a fully illuminated short branch from an eleven-year-oldtree.

FIG. 3 shows an eleven year-old-tree planted on farmland on a sandy loamand annual rainfall of ca. 1200 mm.

FIG. 4 shows bark from the lower trunk of an eleven-year-old tree.

FIG. 5 shows leaves of the clonal cultivar (Shinsei) and its closestvarieties (Eridano, Androscoggin, Oxford) from fully illuminatedbranches of one-year-old cuttings. Top row (from left to right): Upper(adaxial) leaf surface of Shinsei, lower (abaxial) leaf surface ofShinsei. Note moderately cordate base. Bottom row (from left to right):Upper leaf surfaces of Eridano, Androscoggin, Oxford.

BOTANICAL DESCRIPTION OF THE VARIETY

The following description are features described as they appear forexamples of the variety growing in the province of Manawatu, NewZealand. All dimensions in millimeters, weights in grams (unlessotherwise stated). Color chart references are in accord with R.H.S.Color Chart, The Royal Horticultural Society, London (2001 edition).

Young tree

As a young (1-3 years old) tree grown from cuttings in a nursery, theclonal cultivar has a smooth, straight stem form that is circular incross section at the base and becomes slightly angular at the tip. Trunkdiameter typically averages approximately 39 mm in diameter whenmeasured 1400 mm above ground level. Stem color is predominantlygrey-green (near Grey-green 197B) at the base, grading to a light greenat the tip and lenticels (ranging in shape from round to long linear)are very prominent. Branch angle is acute with the branches tending tocurve upwards. Two year old branches (measured at 1400 mm above groundlevel) typically being at an angle of approximately 70° to 50° to thetrunk. The typical average diameter of these branches beingapproximately 12 mm when measured a short distance (100 mm) from theirjoin with the trunk. Branch and trunk surface is smooth in texture and asimilar color (near Greyed-green 197B).

Terminal leaf bud length is typically 20-25 mm and buds are narrow ovatein shape with a narrow acute tip. Color is predominantly green with ared-brown tinge around the bud scale edges. Flower buds are nearGreyed-orange 166A in color. The variety is a male clone, and thestaminate inflorescence, near Red 42A in color, occurs as a pendulouscatkin up to 30 mm in length, with 20-25 stamens.

Leaf color is typically dark-green (near Yellow-green 146A) on the upper(adaxial) surface at maturity and is typically broadly ovate in shape.The base is medium cordate, while the tip is narrow acuminate, and theratio of the length of the midrib to the width of the leaf is small.Length of petiole relative to that of the midrib varies between half tosimilar lengths, and the petiole is light green in color andapproximately 1.1 to 1.9 mm in diameter. The leaf margin is finelyserrate. Hairs are absent from both sides of the leaf and the anglebetween leaf veins and the midrib are acute. The leaf veins are arrangedin a pinnate pattern and are near Green-yellow 1C in color.

Adult tree

Crown width in an open grown situation remains straight andnon-spreading and the trunk is similarly straight. Bark on the lowertrunk is lightly furrowed at this age and light (near Greyed-green 188D)in color. Branches are typically at an angle of approximately 50° to thetrunk.

Mature adult leaf form differs from the juvenile form in that the shapebecomes more ovate-rhomboid due to the leaf base becoming slightlycuneiform or rounded cuneiform and the leaf tip more narrow acuminate.Leaf coloration and margin characteristics remain similar to that of theyoung tree form, as does petiole length relative to midrib length. Veinangle becomes slightly more acute.

Growth Rates

Under nursery conditions height growth from an unrooted 25 cm cuttingcan be expected to reach 2-3 m in the first growing season and after twoyears height will be at least 6 m.

Some indicative field trial growth data are as follows:

TABLE 1 Age Height (m) Diameter at 1.4 m (cm) Planting material 47.1-8.2 7.1-9.5 70 cm unrooted stakes 10 16.4 24.8  3 m unrooted pole

Comparison to closest variety

A number of hybrids involving male P. maximowiczii have been planted inNew Zealand, and these would be the closest varieties to this clone:

P. deltoides×P. maximowiczii ‘Eridano’

P. maximowiczii×P. trichocarpa ‘Androscoggin’

P. maximowiczii×P.×berolinensis ‘Oxford’

Major distinguishing features between this clone and those mentionedabove are crown width in adult trees and shape of leaf base from longshoots of one-year-old cuttings and can be summarised as follows:

TABLE 2 Expression of Expression of Denomination characteristic incharacteristic in of the closest the named Characteristic Shinseivariety closest variety Crown width Straight (narrow) Eridano SpreadingAndroscoggin Spreading Oxford Spreading Shape of Medium cordate EridanoStraight leaf base* Androscoggin Weakly cordate Oxford Straight *fromlong shoots of one-year-old cuttings

Pest and disease resistance

The clonal cultivar shows high resistance to the rusts Melampsoralarici-populina and M. medusae and also to leaf anthracnose Marssoninabrunnea. It also exhibits low palatability to possums (Trichosurusvulpecula).

Plant hardiness

The plant hardiness range (according to the American zoneclassification) has not been determined. However, under New Zealandconditions, the plants are expected to be winter hardy to −30° C. andhave been observed to tolerate temperatures of −6° C. in areas thatexperience some winter cold and frost, and have also been observed togrow well in conditions where summer heat up to 25° C. is experienced.

We claim:
 1. A new and distinct variety (clonal cultivar) of poplartree, substantially as herein described and illustrated, characterisedby a straight, narrow crown form, rapid growth and resistance toMelampsora larici-populina, M. medusae (poplar leaf rusts), Marssoninabrunnea (poplar leaf anthracnose), and low palatability to Trichosurusvulpecula (possum).